The present invention contains a unique combination of active ingredients for topical application. Together, these compounds seem to potentiate their effects and work in a synergistic matter. In addition, the composition of the present invention is prepared in a topical delivery system that enhances skin penetration. The composition is particularly useful for treating hyperpigmentation disorders such as melasma, postinflamatory hyperpigmentation, irregular pigmentation secondary to photodamage, lentigenes (age-spots) and others. The composition is nonirritating to the skin and also provides improved facial skin feel benefits. The unique blend is also useful for conditioning, desquamating, and cleansing the skin. The formulation can be in the form of a leave-on product and/or can be rinsed or wiped from the skin after use. The base uses special preservatives and antioxidants to achieve optimal bioavailability. The unique blend is compromised of vismia and inositol hexaphosphate (phytic acid). Additional ingredients, such as arbutin and kojic acid, may also be included in formulations of the present invention. The overall benefits include lightening pigmentation, providing even skin color and tone, improvement in photodamage and increased clarity. Added benefits include improvement in skin smoothness, radiance and moisture retention.
Cosmetic Interest in Depigmentation and Inhibition of Melanogenesis
The use of skin-lightening cosmetics varies significantly between cultures. In western countries, for example, skin lighteners are applied for the prevention and/or treatment of melasma, freckles and age spots (lentigo senilis). The treatment of irregular hyperpigmentation to reach an even skin tone is, doubtless, the main indication. In Asian and African nations, on the other hand, the primary use of skin lighteners is to make the skin whiter, lighter and brighter. Interestingly, while a tanned look is preferred in the West, most Asian people desire lighter skin. Traditional Asian beliefs hold that white skin denotes nobility and aristocracy. The present invention fulfills the demand of a broad range of these different applications in all continents.
Pigmentation
Pigmentation in animals varies greatly. It is often strikingly beautiful. In birds, most feather coloration is due to the presence of carotenoic pigments. In contrast, most visible pigmentation in mammals results from the synthesis and distribution of the pigment melanin. Chemically, melanins are heterogeneous biopolymers produced by specialized dendritic cells, the melanocytes, which are located primarily in the skin, hair bulbs and eyes. The process by which melanin is formed is known as melanogenesis.
Visible pigmentation in mammals results from the synthesis and distribution of melanin in the skin, hair bulbs and eyes. Tanning, a common and often desired phenomenon in many areas of the world, is simply the result of enhanced melanin production by the skin.
Melanin, the Skin Pigment
Melanin production occurs in the skin within specialized cells known as melanocytes. These cells originate from the neural crest and, during embryogenesis, migrate to various sites throughout the body, including the skin. There they become associated either with the hair follicles or the basal layer of the epidermis.
Epidermal melanocytes are thin, elongated dendritic cells with specific organelles, the melanosomes, which contain all components required for melanin production. The melanocytes, which extend and branch among neighboring epidermal cells, facilitate the transfer of melanosomes. The melanosomes are passed to keratinocytes in skin and to the hair shaft in hair bulbs, where the final distribution patterns of the pigment are determined. This distribution plays an important role in determining color and causes the great variety of colors that occur in the skin, hair, and eyes of humans. In this way, melanin is distributed into the suprabasal regions of the epidermis, where it protects the germinative cells of the basal layer from ultraviolet radiation.
In the human epidermis, each melanocyte is normally associated with approximately thirty-six (36) keratinocytes, together they constitute the epidermal melanin unit. Although melanocyte density varies quite considerably in different regions of the human skin, the total number is relatively constant, even in different racial groups. The average density is between 1'000 and 2'000 melanocytes/cm2 skin.
Melanin plays a crucial role in the absorption of free radicals generated within the cytoplasm and in shielding the host from various types of ionizing radiation, including ultraviolet (UV) light. Thus, melanin protects the skin against sunburn, actinic damage and cancer. Moreover, melanin can act as a thermoregulator by absorbing different forms of energy and dissipating them as heat. Melanins are comprised of two basic types: eumelanins, which are brown or black, and phaeomelanins, which are red or yellow. In mammals, mixtures of both types are typically found. Interestingly, phaeomelanin has the capacity to produce free radicals in response to UV radiation. Since free radicals can inflict cell injury, phaeomelanin may actually contribute and intensify UV-induced skin damage, rather than protect the skin.
Melanogenesis Overview (FIG. 1)
The initial compound for the production of melanin, both the brown-black eumelanin and the yellow-red pheomelanin, is the amino acid tyrosine. The quantity of melanin synthesized is thus proportional to the amount of tyrosine activity present in the cell. Melanin synthesis starts with the hydroxylation of tyrosine to 3,4-dihydroxyphenylalanine (L-DOPA) (see FIG. 1). This hydroxylation is the rate-limiting step in the melanogenesis pathway and is catalyzed by the key regulatory enzyme: tyrosinase. In humans, evidence indicates that human skin color can be correlated with tyrosinase activity.
Tyrosinase is the rate-limiting, essential enzyme in the biosynthesis of the skin pigment melanin. As such it catalyzes three different reactions in the biosynthetic pathway of melanin:                The hydroxylation of tyrosine to 3,4-dihydroxyphenylalanine (DOPA)        The oxidation of DOPA to DOPA-quinone        The oxidation of 5,6-dihydroxyindole (DHI) to indole quinone        
Tyrosinase is a multi-functional, glycosilated, copper-containing oxidase with a molecular weight of approximately 60 to 70 KDa. In mammals, it is exclusively found in melanocytes. It is therefore a good marker for melanocytes. Tyrosinase is encoded by a gene at the c-locus that maps the chromosone 11q-14-q21 in humans and chromosone 7 in mice.
Tyrosinase is expressed specifically in pigment-producing cells. Expression of tyrosinase is regulated by cyclic AMP (cAMP). Tyrosinase is formed within the Golgi apparatus of the melanocyte by melanosomal ribosomes, tyrosinase glycosilation occurs in the endoplasmic reticulum in route to the TNGN (Trans-Golgi Network) and is transferred to the melanosome in its first stage of development (Stage I). Tyrosinase and additional proteins are assembled in Stage II melanosomes.
The molecular basis of Oculocutaneous Albinism (OCA) results from mutations in the genes that encode tyrosinase. In OCA type 1A, mutations in both copies of the tyrosinase-encoding gene lead to complete loss of enzyme activity, no melanin is found in the hair, skin or eyes, also known as albinism.
Recent studies have shown that mammalian melanogenesis is not regulated solely by tyrosinase at the enzymatic level and additional melanogenic factors have been identified, which can modulate pigmentation in either a positive or negative way. They have been called Melanogenesis-Related Proteins (MRPs) and are structural proteins involved in the formation of melanosomes together with the enzymes involved in the transformation of L-tyrosine to melanin: tyrosine in addition to tyrosinase related protein-1 (“TRP-1”), tyrosinase related protein-2 (“TRP-2”), gp 100 and PMEL 17, MART-1/Melan-A, P-protein MITF and MSH receptor.
The rate limiting steps in melanogenesis are the hydroxylation of tyrosine in the initial chemical reaction (conversation of tyrosine to DOPA), and the oxidation of DOPA by DOPA oxidase/tyrosinase (see FIG. 1) in the second reaction. In the last thirty (30) years, it has been demonstrated that there are additional control points in the melanin biosynthetic pathway. An example is the reaction that occurs when DOPAchrome is converted to 5,6-dihyroindole-2-carboxylic acid (DHICA) by TRP-2, also known as dopachrome tautomerase.
Dopaquinone is converted by a series of complex reactions involving cyclization and oxidative polymerization, which finally result in the formation of eumelanin. It was once thought that these latter reactions occurred spontaneously, but it now appears that certain steps are under regulatory control. For instance, there is now evidence that dopachrome can be converted to either 5,6-dihydroxyindole or the carboxy derivative 5,6-dihydroxyindole carboxylic acid (DHICA). The latter step appears to be catalyzed either by metal ions or by a recently discovered enzyme, dopachrome tautomerase, also known as TRP-2.
Dopachrome tautomerase occurs in melanosomes complexed with tyrosinase and perhaps other melanosomal membrane proteins. In addition, peroxidases can utilize DHI as a substrate and thus may also play a role in melanogenesis.
Another control point in the melanin biosynthetic pathway involves Tyrosine-Related Protein 1 (TRP1). Mutations in both copies of the TRP1 gene lead to OcularCutaneous Albinism (OCA) type 3, resulting in partial melanin loss. In mice and humans, TRP1 stabilizes tyrosinase and also in mice functions as DHICA oxidase.
The switch of the synthetic pathway from eumelanin to phaeomelanin requires the presence of sulphydryl residues. Thus, if dopachrome encounters either cysteine or glutathione, cysteinyl DOPAs are formed. These are then quickly oxidized into benzothiazines and subsequently to phaeomelanins.
Regulation of Melanogenesis
The regulation of pigmentation in mammals is controlled at many different levels and is quite complex at each level. Melanocytes are initially derived from the neural crest and migrate throughout the embryo during development. These migration patterns are under strict genetic control and can lead to some interesting patterns when the final melanocyte distribution in the skin is not uniform, as can be seen in zebras and giraffes. Pigmentation is also regulated at the cellular level by melanocytes synthesizing melanin within melanosomes, which can be produced in varying sizes, numbers and densities. Lastly, melanogenesis is regulated at the subcellular level where the synthesis and expression of various melanogenic enzymes and inhibitors play a critical role.
Skin pigmentation depends upon the organization and functioning of the epidermal melanin unit and several separate, but related, events:                Melanoblast migration from the neural crest        Melanoblast differentiation into melanocytes        The rate of synthesis and melanization of melanosomes        The size of melanosomes        Synthesis of melanin        The efficacy of melanosome transfer into keratinocytes        The rate of melanosome degradation within the keratinocytes        The rate of synthesis, inhibition and decay of tyrosinase        Activity of tyrosinase in melanosomes        
Melanocytes work in close harmony with their neighboring cells in the epidermis. They are influenced by a variety of biological factors, including interleukins, interferons, growth factors, vitamins and prostaglandins, which determine not only whether melanin is synthesized, but also what type of melanin is produced. Presumably, these factors provide the complex signals that stimulate pigmentation after trauma, UV-exposure, or other environmental stimuli that induce the melanocyte-stimulating hormone (MSH, or melanotropin), a peptide produced by the posterior pituitary. Once MSH binds to melanocyte surface receptors, a dramatic, up to 100-fold, increase in melanogenesis results.
Melanogenesis can be affected at three different time intervals (see FIG. 2):    1. Before melanin synthesis by inhibiting transcription or glycosilation of the enzymes, thereby producing an alteration of the structure or function of the melanosome;    2. During melanin synthesis and when melanosomes are mature, peroxidase, ROS scavengers, reduction agents and/or lipids directly inhibit tyrosinase. This would affect the uptake and distribution of melanosomes in recipient keratinocytes.    3. After melanin synthesis, melanin and melanosome degradation occurs, increasing turnover of pigmented keratynocytes. Any blockage at this level would inhibit melanosome transfer and dispersion of melanin.
Recent work on molecular mechanism regulating pigmentation suggests that cAMP PKA (cyclic AMP dependent protein kinase) is the second major intracellular signaling molecule critical for skin pigmentation. PKC β (protein kinase C beta) is a key activator of tyrosinase, acting through phosphorylation of the protein at the cytoplasmic domain. Data suggest that this might be the rate limiting step. Cross talk between C-AMP and PKC affects pigmentation by up-regulating the expression of PKC-β.
The cyclic AMP pathway plays an important role in the production of melanin and the regulation of melanogenesis. The cyclic AMP pathway in melanocytes is activated by: ACTH, α-MSH, endothelin 1, nitrous oxide (NO) and PGE2. At the end product site, in response to UV stimulation, the keratinocytes secrete factors, such as interleukin 1α, interferon and TNFα. These factors inhibit melanogenesis.
Inositol Mechanism of Action
The nature of trying to lighten skin requires the use of new agents or means with little to no toxicity.
Inositol exists in plants as phytic acid (inositol hexaphosphate) and is also present in avian and fish erythrocytes, where it plays a role in allosteric regulation of oxygen affinity to hemoglobin. Inositol is an essential element in many species, including humans.
Biologically, inositol is an essential component of the cell membrane and is a key component of the multiple system intracellular signaling pathways and has also been implicated in key roles in the immune system.
Inositol functions on the site-specific signals on the cell membrane activating proteins for the assembly of spatially localized functional complexes, including signal transduction, cytoskeletal and membrane trafficking events with subsequent formation of specific proteins.
Although inositol has been implicated in many different functions and uses, it has not been described or used as a lightening agent. Its effect on pigmentation or melanogenesis has not been reported or documented.
We believe that inositol is a new lightening agent and works by affecting melanogenesis, acting in the melanin pathway.
Inositol may act in the melanogenesis pathway as an inhibitor through several different mechanisms. For example, it is possible that inositol acts as a transcription inhibitor by increasing the amount of dose-dependant intra-cellular free calcium (Ca++) in the endoplasmic reticulum, where tyrosine is glycosilated. This would result in faulty protein production affecting the function and structure of the melanosomes.
Once melanin is glycosilated at the endoplasmic reticulum, the formed proteins are transported in vesicles to the TGN (Trans-Golgi Network) and from the TGN to the melanosomal compartment. A number of proteins help in the formation and transport of these vesicles including guanosine triphosphate-binding proteins, such as rab7 and phosphatidyl inositol kinase. Phosphatidyl inositol also regulates the membrane trafficking of melanosomal glycoproteins, controlling the production of melanin by down-regulating its substrate.
It is also possible that inositol acts as a post-transcriptional inhibitor of melanogenic enzymes at the N-glycosilation level. This would affect the protein structure of these enzymes and eventually the intracellular transport of the melanosome, reducing the level of its expression.
As mentioned earlier, melanogenesis results from a variety of regulatory processes involving direct effects of UV radiation on the melanocyte and indirect effects through the release of its final product (down-regulation). One of the intracellular signalling pathways is cyclic AMP. This pathway plays an important role in the production of melanin and the regulation of melanogenesis. The cyclic AMP pathway in melanocytes is activated by: ACTH, a-MSH, endothelin 1, nitrous oxide (NO) and PGE2. At the end product site, in response to the UV stimulation, the keratinocytes secrete factors, such as interleukin 1α, interferon and TNFα. These factors inhibit melanogenesis. Inositol hexaphosphate increases cyclic AMP and thereby decreases the production rate of melanin. A balance between these keratinocyte factors permits melanocyte growth and differentiation, ultimately controlling skin pigmentation.